The decay of93g Ru,93m Ru,91g Mo,91m Mo,91g Tc and91m Tc

Decay studies on a number of short-lived odd nuclei in theN=50 region are described. The 59.6-s ⁹³Ru ground state decay was studied in detail for the first time; in these experiments the 10.8-s activity^93m Ru was discovered. The⁹¹Tc activities were also observed for the first time. The ground state and an isomeric state of this nucleus decay with nearby equal half-lives (3.14 and 3.3-min). The activities^91g Mo (16.6-min) and^95m Mo (65.1-s) have been reinvestigated. A number ofγ-rays, previously erroneously assigned to the⁹¹Mo activities, could be eliminated. A strong similarity is noted for the decay schemes of theN=49 isotones^91m Mo and^93m Ru. The energy of the 1/2^? isomeric state in⁹³Ru and theB(M4)-value of the isomeric transition fit well into the systematics of the previously knownN=49 isotones.     

Adsorption of CO on the (110) plane of tungsten electron impact,thermal desorption,and work function measurements

The adsorption of CO on the (110) plane of tungsten has been studied using electron impact desorption, thermal desorption, and work function measurements in a single apparatus combining these various techniques. It is concluded that a single molecular adsorption state exists at 20–250 K (virgin-CO). At 300–400 K, 60% of the low temperature layer desorbs, the remainder converting principally to a beta-1 state, which has very small electron impact cross section; in addition to beta-1 an O⁺ yielding state, which we call beta-precursor is formed. The beta-1 state is stable to 900 K, where some desorption and conversion of the remaineder to a beta-2 state occurs. The O⁺ yielding state decays with increasing T and is gone at 800 K. Readsorption on beta-1 leads to two types of adsorption states called alpha and gamma, which seem to be site specific. Electron impact desorption yields mostly CO⁺ and CO for virgin, O⁺ for beta-precursor, and CO⁺ and CO for the readsorption states. There is no isotopic mixing in virgin or in readsorbed CO, nor does readsorbed CO exchange with beta-1 or beta precursor. There is complete isotopic mixing in beta desorption. In addition, massive EID creates another state, characterized by a large dipole moment, also yielding O⁺ in EID. This state can be converted to beta-1 by heating to 400 K. The total disappearance cross sections for the various states are virgin-CO5 × 10^?17cm²; γ-CO 1.6 × 10^?16cm²; α-CO 5 × 10^?17cm²; β-precursor 6 × 10^?18cm²and 1.2 × 10^?19cm²; EID induced state 8 × 10^?18cm². In addition, cross sections for ion production are determined and found to be several orders of magnitude less than total disappearance cross sections. These results, and Leed and coverage data obtained in parallel investigations are used to formulate models of the various adsorption states. It is concluded that virgin and readsorbed CO are molecular and beta-precursor and beta dissociated, although strong interactions between C and O remain. The electron impact desorption of physisorbed CO was investigated and found to yield C⁺, O⁺, and neutral CO, but very little CO⁺. These results suggest primary dissociation of CO by electron impact, and desorption of neutral physisorbed CO by the energetic fragments. Physisorbed CO⁺, although undoubtedly created, lies on the attractive part of its potential curve relative to the surface, and thus does not desorb as CO⁺.     

Accurate rotational spectroscopy of sulfur dioxide, SO2, in its ground vibrational and first excited bending states, v2 = 0, 1, up to 2 THz

Approximately 150 pure rotational transitions each have been recorded for SO₂, v₂ = 0 and 1, in selected frequency regions up to 2 THz. The J and K_a quantum numbers reach very high values: 92 and 23, respectively, for the ground vibrational state and 81 and 21, respectively, for the first excited bending state. The highest levels accessed are almost 3000 cm⁻¹ above ground. The relative experimental uncertainties Δν/ν are about 10⁻⁸ for several medium to strong, isolated lines, and generally better than 2.5 × 10⁻⁷. Improved spectroscopic parameters have been obtained for both states, particularly for the excited bending state. In fact, the accuracies with which the energy levels of the v₂ = 1 state are known depend essentially only on the accuracy with which the vibrational spacing is known from infrared spectroscopy.     

Electric quadrupole moments of the K π = 8− and 23/2− isomeric states in 170, 171, 172Hf

The spectroscopic quadrupole moments of the K ^π = 8^? isomers in ¹⁷⁰Hf and ¹⁷²Hf, Q _s ?=?4.91(17) b and 5.40(19) b, respectively and Q _s ?=?4.92(17) b for K ^π ?=?23/2^? in ¹⁷¹Hf have been measured using the time differential perturbed angular distribution technique. The nuclear reaction ¹⁶⁰Gd(¹⁶O, xnγ) was used to excite the respective isomeric states and for the recoil implantation of Hf nuclei into the Hf foil. The quadrupole deformation for the 8^? isomer and the ground state has the same value. The deformation corresponding to 23/2^? isomeric state is observed to be reduced with respect to the ground state due to the i _13/2 neutron alignment. The results are in good agreement with the multi-quasiparticle calculations.     

Ensemble Steering, Weak Self-Duality, and the Structure of Probabilistic Theories

In any probabilistic theory, we say that a bipartite state ω on a composite system AB steers its marginal state ω ^B if, for any decomposition of ω ^B as a mixture ω ^B =∑ _i p _i β _i of states β _i on B, there exists an observable {a _i } on A such that the conditional states $\omega_{B|a_{i}}$ are exactly the states β _i . This is always so for pure bipartite states in quantum mechanics, a fact first observed by Schrödinger in 1935. Here, we show that, for weakly self-dual state spaces (those isomorphic, but perhaps not canonically isomorphic, to their dual spaces), the assumption that every state of a system A is steered by some bipartite state of a composite AA consisting of two copies of A, amounts to the homogeneity of the state cone. If the state space is actually self-dual, and not just weakly so, this implies (via the Koecher-Vinberg Theorem) that it is the self-adjoint part of a formally real Jordan algebra, and hence, quite close to being quantum mechanical.     

The rotational spectra of the 79, 69, and 7 vibrational states of nitric acid

The rotational spectra of the first three vibrational states of nitric acid above 1000 cm⁻¹, 7¹9¹, 6¹9¹, and 7², have been measured and analyzed. The 7² state, along with the previously published 7¹ state, show the rotational and centrifugal distortional constants have a near linear dependence on the υ₇ vibrational quantum number. Large changes for several centrifugal distortion constants of the υ₇ = n series of states are attributed to a c-type Coriolis resonance manifold between the ν₇ and ν₆ vibrational modes and the Hamiltonian reduction and representation used to fit the spectra. The 7¹9¹ and 6¹9¹ states have torsional splittings of 12.361(8) and 22.47(1) MHz, respectively. These splittings are large compared to 2.340(8) MHz of the 9¹ state and can be explained by a ∼1-2% mixing through anharmonic Fermi resonances with the 9³ state, which has a large torsional splitting of ∼1760 MHz. The millimeter/submillimeter-wave spectrum of each state was fit separately to the experimental uncertainty of the measurements. The resultant rotational constants, distortional constants and inertial defects agree well with DFT calculations.     

83mKr, a potentially powerful PAC probe

In the decay of ⁸³Rb to ^83mKr and the subsequent decay to the ⁸³Kr ground state a 553–9.4 keV γ-γ and a 17.85–9.4 keV e^?-γ cascade are populated. The intermediate 9.4 keV 7/2^?+? state with a half-life of 154 ns is a perfect candidate for the application of the perturbed angular correlation (PAC) technique. Thus, it is possible to investigate the lattice environment of the implanted probes via the electric quadrupole interaction of the 9.4 keV 7/2^?+? state with the electric field gradient produced by the host lattices. Details of the production of this new PAC probe and planned measurements will be discussed.     

Studies of 158, 160, 162, 164, 166Dy levels with the (t,p) reaction

Angular distributions of the ^{156, 158, 160, 162, 164}Dy(t, p) reactions have been measured using 17 MeV tritons from the McMaster University Tandem Van de Graaff accelerator. The reaction products were analyzed with a magnetic spectrograph and detected with photographic emulsions, resulting in overall peak widths of 15–20 keV (FWHM). Levels populated with L=0 transitions were identified from the unambiguous angular distributions, and at least one previously-unknown I^π = 0⁺ state was found in each nuclide studied. New I^π=0⁺ levels were found at energies of 1269, 1549, 1743, and 2000 keV in ¹⁵⁸Dy, 1457 and 1709 keV in ¹⁶⁰Dy, 2126 keV in ¹⁶²Dy, 1774 keV in ¹⁶⁴Dy, and 1149 keV in ¹⁶⁶Dy. Also, the previously proposed 0⁺ assignment for the 1655.4 keV level in ¹⁶⁴Dy has been confirmed. For the neutron-rich nuclide ¹⁶⁶Dy there was previously no information on excited states listed in the Nuclear Data Sheets, and many levels have been located in the present study, including the gamma band and an excited K^π=0⁺ band. The 1457 keV 0⁺ state in ¹⁶⁰Dy is a possible candidate for the bandhead of the previously reported S-band. The fraction of the L=0 strength which feeds excited states is unsually high in several cases, and particularly for ¹⁶⁴Dy, in which the total L=0 strength to excited levels is ∼35% of that for the ground state. This can be explained qualitatively in terms of a “sub-shell closure” corresponding to the gap in the Nilsson diagram at N=98, and supports the earlier explanation of large L=0 strengths to excited states in the ¹⁶¹Dy(t, p) ¹⁶³Dy reaction as being due to this gap. Most of the L^π=0⁺ excited states observed in previous (p, t) studies were not populated in the present work, thus ruling out a pairing vibrational interpretation for these levels.     

Excited states of 10B from the 6Li(α, γ) and 9Be(p, γ) reactions

Excitation functions for the (α, γ) and (p, γ) reactions leading to ¹⁰B have been measured at θ = 0° in the energy range from E_x = 6.7 to 7.6 MeV. Two resonances corresponding to levels at 6.88 and 7.44 MeV are observed. Branching ratios extracted from γ-ray spectra are the same in both reactions for the 6.88 MeV (1^?, T = 0 + 1) level, but different at 7.44 MeV. The T = 0 + 1 level at 7.44 MeV (Γ = 90±10keV) is assigned 2^? or 2⁺ from its strong branch to the 3⁺ ground state. We find no evidence for a second isospin mixed 1^? state.     

Thermal neutron induced α-particle reaction on64, 65, 67Zn and77Se

The (_n th,α) reaction spectroscopy was done on^{64, 65, 67}zn and⁷⁷Se at the 87 m curved thermal neutron guide of the Grenoble high flux reactor. In each of the⁶⁴Zn(n, α)⁶¹ Ni and⁶⁷ Ni(n, α) ⁶⁴Ni reactions, one line showed up corresponding to anα-particle transition to the first excited state in⁶¹Ni and⁶⁴Ni withσ _α1=11±3 μb and 159±20 μb respectively. In the case of the radioactive⁶⁵Zn(T _1/2=244d) nucleus, two lines showed up corresponding to the ground state and the first excited state transitions in⁶²Ni with large values ofσ _α0=1.0±0.1b andσ _α1=1.0±0.1b. For the⁷⁷Se(n, α)⁷⁴Ge reaction, the ground state and first excited transitions were present withσ _α0=940±20 μb andσ _α1 = 30±5 μb respectively. The spin-parity (J ^π) of the neutron resonance contributing at thermal energy are discussed.     

Decay of90m,g Rb

The decay of mass separated⁹⁰Rb has been studied usingβ,γ and conversion electron spectrometers in single and coincidence modes. The half-lives of the ground state and the isomeric level have been confirmed to be 162± 3 and 258±4 s, respectively. Theγ-rays from the decays of ground state and metastable state have been identified by measuring the decay of individual photopeaks using Ge(Li) detectors. The multipolarity of the 106.6 keV isomeric transition has been determined to beM3. Separate decay schemes of the ground and metastable states are presented. The levels of⁹⁰Sr are discussed in terms of the available experimental and theoretical information. Radioactivity.^90m,gRb [from²³⁸U(p, f)]; measuredT _1/2,E _γ,I _γ,γ—γ coin,I _ce,cc,E _β deduced logft,⁹⁰Sr levels, mass separated⁹⁰Rb.     

Two-particle,two-hole Jπ=0+ states in 40Ca

Excited J^π=0⁺ states in ⁴⁰Ca have been identified by the observation of L=0 angular distributions in the ³⁸Ar(τ, n) ⁴⁰Ca reaction. Strong transitions are observed to the ground state, the known 2p–2h at 9.38 (T=1) and 11.98 MeV (T=2), and to states at 8.28 and 10.65 MeV. The strongest excited-state transition is to the 8.28 MeV state, which we identify as the 2p–2h T=0 state. The J^π=0⁺ state at 7.30 MeV which has been suggested as the 2p–2h T=0 state is not observed.     

The46Ti(d,τ)45Sc reaction

The⁴⁶Ti(d, τ)⁴⁵Sc reaction has been investigated at an incident energy of 52 MeV. Angular distributions have been taken for 14 τ-groups corresponding to excitation energies below 4 MeV in⁴⁵Sc. Spectroscopic factors were extracted through DWBA calculations. Spins and parities of 5/2⁺ are proposed for states at 1.30, 1.80, 2.91, 3.48, and 3.72 MeV. The hole state spectrum of⁴⁵Sc closely resembles that of⁴⁷Sc. A strong fractionation of the 1d _3/2 strength was not observed in contrast to other recent work. The data provide evidence for (1f _7/2 · 1f _5/2 ¹) components in the ground state wave function of⁴⁶Ti, which demonstrates that such configurations are not restricted to neutron excitations.     

Feasibility Study of D(3H,3He)nn Experiment Searching for nn Ground State

Possibility of existence of nn ground state was discussed in 2011 by H. Witala and W. Glöckle based on anomalous enhancement of nn QFS (Quasi-Free Scattering) cross section in nd breakup at E _n = 26 MeV reported in 2002. To search for the nn ground state, we have made a feasibility study of D(³H,³He)nn and D(n, p)nn experiments. ³H and n secondary beams are produced respectively by D(d,³H)p and D(d, n)³He reactions at forward angle, and are injected on a CD₂ foil target. If an nn ground state exists, a single peak is observed in the ³He and p energy spectra. We conclude that these experiments are feasible.     

Ab initio potential energy curves and vibrational levels for the c, l, and i states of the hydrogen molecule

Potential energy curves for the hydrogen molecule in the c³Π_u, I¹Π_g, and i³Π_g state have been calculated in the Born-Oppenheimer approximation. Highly flexible wavefunctions have been used, and for each state the calculations have been carried out for 40 different internuclear distances in the region 1 ≤ R ≤ 12 a.u. For the Π_g states the wavefunctions are known to change their character around R = 5 a.u. The effect of this change on various components of the energy has been analyzed. The vibrational Schrödinger equation for all states has been solved for H₂, HD, and D₂. For H₂ the resulting energies are compared with the experimental values and it is shown that the adiabatic effects are likely to be responsible for the existing discrepancy between the theoretical and experimental values.     

Two-center molecular states in9B,9Be,10Be,and10B

The molecular states in the mass 9 and 10 nuclei, which consist of two α-particles plus one or two valence nucleons (protons or neutrons) are discussed. Arguments for the existence of two-center dimers as excited states in¹⁰Be and corresponding resonances (p+⁹Be) in¹⁰B are given. The latter states are observed as anomalous (non statistical) population in the final state interactions in thep+⁹Be channel in various heavy ion collisions. With the establishment of two-center states (dimers) based on the αα-potential and a localized binding via two nucleons in¹⁰Be, the existence of more extended structures (multimers) by adding (α2n) structures to¹⁰Be* is postulated. Generally clustering intoα-particles and nucleons in terms of molecular states is expected to occur at excitation energies close to the threshold for these substructures in analogy to the clustering rules of Ikeda forα-particle nuclei. Consequences to clustering properties of neutron rich nuclei are discussed.     

Resonant structure observed in the 3He(τ, γ)6Be capture reaction

The ³He(τ,γ)⁶Be capture reaction has been studied for ³He bombarding energies from 12 to 27, MeV. Transitions to the first excited state in ⁶Be(T = 1, 2⁺) are readily seen. Transitions to the ground state in ⁶Be (T = 1, 0⁺) are very weak and their presence could not be ascertained. The 90° excitation function for these transitions shows a broad maximum centered at E_τ = 23 ±1 MeV. This is interpreted as a resonance in the compound nucleus ⁶Be at E_x = 23.0±0.5 MeV with a configuration other than ³He+³He. These results are compared with other experimental work as well as with theoretical predictions.     

Semiclassical method for calculating the energetic values of helium, lithium and beryllium atoms

In previous papers we have presented a wave model for conservative bound systems resulted from the equivalency between the Schrödinger and wave equations. We proved that the normal curves of the characteristic surface of the wave equation, denoted by C curves, are solutions of the Hamilton-Jacobi equation, written for the same system, and correspond to the same constants of motion as those resulting from the Schrödinger equation. In this paper we present a method for computing the energetic values of conservative bound systems which is based on the properties of the C curves. The method is applied to the 1s ² state of helium, 1s ²2s and 1s ²2p states of lithium and 1s ²2s ² state of beryllium. Our theoretical values are compared with experimental data taken from well-known books. The relative error of our method is less than 5 x 10^?3.